1. Field of the Invention
The invention relates to a monitoring and/or control device having an assembly of system modules in the form of field bus coupler modules, supply modules and/or input/output modules, which are arranged adjacent to one another and have terminal contacts in order to connect a system bus and/or a voltage supply terminal of a system module to the subsequent system module.
2. Description of the Related Art
Such monitoring and/or control devices are known, for example, for programmable logic controllers (PLCs) or process monitoring systems and are described in DE 44 02 002 A1. System modules which each have a dedicated housing having electrical connection terminals which are accessible from the outside are plugged onto a common top-hat rail. The system modules are arranged adjacent to one another on the top-hat rail, associated electrical contact terminals of mutually adjoining system modules being connected to one another. In this manner, voltage supply lines are realized, via which voltage is supplied to the connected system modules starting from a regulated switched mode power supply (voltage supply module) which is generally arranged on the left-hand side on the top-hat rail. In a corresponding manner, a system bus is realized by the electrical contact terminals which is fed via a field bus coupling module from the left-hand side. The field bus coupling module is used for coupling the internal system bus to an external field bus.
The advantage of this first design is that the line length of the supply lines and the system bus is determined by the system modules themselves, and no separate lines are required.
A second design, which is described, for example, in D. Tschimpke: “Flexibilität zahlt sich aus”, [flexibility pays off] in elektro AUTOMATION [electro automation], April 2005, pp. 2+3, envisages that the system bus and/or the voltage supply lines are implemented on the top-hat rail. The system modules have contact pins for making contact with the system bus lines and voltage supply lines. However, this has the disadvantage that the top-hat rails are relatively complex, and the line lengths are not matched optimally to the actually required line lengths. This may result in unnecessary attenuation losses. In addition, the system bus lines and voltage supply lines are accessible from the outside and are subject to a potential risk of interference.
In the implementation of the system bus and/or the voltage supply line using the first design with connection terminals at the system modules for the further connection of the system bus or the voltage supply line to an adjacent system module, there is the problem that the system bus and the voltage supply line is interrupted by a system module in a sequence of system modules being removed.
Hot-swappable systems are required for automating processes in which the replacement of individual electronic components should not result in the entire system coming to a standstill. The reason for the replacement may be a defect in an individual electronic component or the need for a modification.